A power factor correction circuit is usually of a boost converter and comprises an inductive storage element, a rectifier arrangement connected to the inductive storage element, for providing an output voltage, and a switch connected to the inductive storage element. The switch controls the current drawn by the inductive storage element on the basis of the output voltage and is connected up such that the storage element absorbs energy via input terminals, and is magnetized as a result, when the switch is closed, and outputs the absorbed energy to the rectifier arrangement, and is demagnetized as a result, when the switch is subsequently opened.
A switching converter of this kind can be operated with continuous current draw or with discontinuous current draw (Discontinuous Current Mode, DCM). The mode of operation with continuous current draw is also called non-intermittent operation, whereas the mode of operation with discontinuous current draw is also called intermittent operation. In the case of non-intermittent operation, the switch is switched on again, during a demagnetization phase of the inductive storage element, when the storage element is fully demagnetized. In the case of intermittent operation, a waiting time is waited after complete demagnetization before the switch is switched on again.
A power factor correction circuit operating in intermittent mode is described in DE 103 55 670 B4.
During the waiting time after complete demagnetization of the inductive storage element and before the switch is switched on again, oscillations may occur which are caused by an LC resonant circuit which comprises the inductive storage element and parasitic capacitances, particularly a parasitic capacitance of the switch. These oscillations decay more slowly the higher the quality of the inductive storage element used.
These oscillations can result in distortions in the average current draw, which is intended to be proportional to an applied input voltage in the case of a power factor correction circuit. Depending on the phase angle of the oscillation at which the switch is switched on again, the energy absorbed by the inductive storage element may vary from actuation period to actuation period, even at a constant input voltage, which results in distortion of the current draw.